User blog comment:Semerone/Translation test BR (2)/@comment-30866325-20180626213532/@comment-30866325-20180626213909

Of cause, "Guren" (ぐれん) can also mean "Anger", but in this constellation of Kanji, it refers to Zenki's Crimson Lotus Attack from the manga.

As such, your assumption of these being related to the manga and the anime is correct.